1. Field of the Invention
The present invention relates to a container consisting of a body and a bottom plate of cardboard laminated with a plastic material, and a method and a device for manufacturing the same.
More particularly, the present invention relates to a container in which the side superimposed portion of the container is completely adhered to a distance of 2 to 3 mm from the upper end, and the upwardly folded portion of the lower end of the body is adhered to the downwardly folded portion of the periphery of the bottom plate; and to a method and a device for manufacturing the body and the bottom plate of such a container.
2. Description of the Prior Art
Plastic laminated paper sheets have conventionally been used for containers for holding liquids. In many such containers, juices, rice wine or the like are exposed to portions laminated with paper sheets, aluminum foils, synthetic resin, or the like for facilitating flowability of the content of the container at room temperature, and the containers are sealed with film-shaped lids. In general, the liquid must be heated to a high temperature for heat-sealing the container. In such a case, when 2 to 3 mm of the side superimposed portion from the upper end of the cup is not completely adhered, the contents seep from the upper end of the cup to the outside under capillary action. This hinders the heat-sealing of the lid and results in incomplete sealing. This permits leakage of the contents to the outside, introduction of air, and so on. Thus, this container is unsuitable as a container for holding liquids which are flowable at room temperature. The superimposed portion of a blank is generally sealed linearly in a certain width. However, as shown in FIG. 2, when viewed from its section, a sealed portion a does not extend to the inner end surface. In this figure, numeral 1 denotes a cup body and 2 is a superimposed portion at both ends of the blank of the body. In some cases, the side end of the blank which comes inside the container is skived to a certain extent from the outside. The unskived portion is folded outwardly, and the side ends of the body are superimposed on each other and sealed so that only the portion of the body which is laminated with polyethylene is brought into contact with the liquid inside the container. Thus, the permeation of the liquid when the side edge is cut and exposed to the liquid is eliminated. In any case, in a conventional cup-shaped sealed container for holding liquids, the sealed portion is as shown in FIG. 2. Since the liquid inside the container is at a high temperature when the lid is heat-sealed, the liquid permeates by capillary action to the outside from an unsealed portion b. This hinders the heat-sealing and has presented problems in the manufacturing procedure.
Conventionally, when adhering the side superimposed portion of the container body for forming the body, the contacting surface of an ultrasonic horn to the upper side superimposed portion is flat. However, when the side superimposed portion is adhered with such a conventional ultrasonic horn, the adhesion gradually weakens from the center of the horn contacting surface toward the outside, and the adhesion of both ends, especially the portions 2 to 3 mm from the ends, is not complete. When an attempt is made to completely adhere these portions, problems arise such as cracks at the central portion of the side superimposed portion.
A device has conventionally been used for hot-pressing the bottom plate of the container. The device consists of an outer press mold for receiving the adhering portion of the lower end of the container body and the periphery of the bottom plate, and further consists of a knurling tool rotating inside the outer press mold. Since there are a number of recesses and projections at the portion of the knurling tool which is brought into contact with the above-mentioned adhering portion in the direction of rotation of the knurling tool, cracks form there, leading to leakage of the contents and so on.